Water companies: water treatment works discharge limits for environmental permits

Find out about discharge limits and controls of substances discharged from water treatment works.



This guide is for operators of water treatment works (WTW).

The Environment Agency regulates WTW by assessing the quality of the effluent they discharge against set compliance limits.

This guide explains how we control and set limits at WTW for:

  • chlorine
  • aluminium
  • polyelectrolytes
  • suspended solids – including granulated activated carbon fines
  • iron
Published 8 May 2018